My take, as explained in the comments there, is that it all boils down to the motive of the photographer. If the same shots had been captured by security cameras, they would feel less creepy, even though they too would have been shot in a public place, with no awareness from the subjects, without asking their permission. However, the camera has no mind of its own, so the subjects and activities it captures cannot have sprung from impure motives.
Of course, there could be a person posting these pictures online after going through security camera footage, but that doesn't seem to matter as much. He's just passing along images that were recorded by something else -- something cold and devoid of emotion, and hence lacking any motive.
And who knows, maybe someday soon they'll have an automated computer program that randomly chooses a scene from a security camera and posts them to a tumblr. It would probably be approved first by a person just to make sure there was something worth viewing in the shot, rather than an empty street at night. But that would remove yet another source of human motive from the shooting-and-distributing of random public pictures.
In short, giving others evidence of having a red-blooded male libido is incriminating. You've proven that you're a perv, a creep, a stalker, a date-rapist. The case of creepshots is just one example of a much broader pattern of moral panic about the dangers that the male sex drive poses to society in general, and to women in particular.
So, contrary to all the feminazi indignation about the "sexual double standard," men are now judged and condemned by an even more obsessive paranoia. Women don't have to defend having a promiscuous sex life anymore, or cohabiting before marriage, and neither do men. But girls can't come right out and say that they like boys and that they like sex -- that crosses the "slut" line. It's motives and intentions that count more than behavior and outcomes.
(Hence also the OK-ness of a girl getting into a drunken random hookup -- it's not like she intended to have sex with a perfect stranger, it just happened when neither of them were much aware of or in control of their mindset and behavior.)
If there were truly a sexual double standard favoring men, then they could express their healthy sex drive with impunity (funny how we have to talk about it like it's a potentially criminal thing these days, eh?). But the days when you could publicly comment on girls' bodies to your buddies are long gone.
A couple months ago I was walking by a construction site on campus, and one of the workers was about to say something like -- I'm inferring -- "get a load of the sweet ass on that chick!" But his fellow construction workers waved him off and told him not to, albeit in a friendly way like "Hey, we're just trying to look out for your security -- you don't know what they'd do to you if you made that kind of comment these days."
Guys for the past 20 years have been way more concerned with and desperate to prove their non-rape-y motives before a society-wide jury. An unapologetic song like "Sexual Healing" could never make it with audiences these days. Girls don't feel comfortable admitting to having a healthy sex drive (for the minority who still do feel that way), but it's not as though they'd be thrown into a kangaroo court of public opinion and have their motives scrutinized.
It'd just be some mild slut-shaming: "Gosh, someone's feeling a little slutty, aren't they?" or "Since when did the town slut move into this neighborhood?" Not as though they'd be expected to apologize and prove that they were willing to change, as though their libido threatened the foundations of society, or the well-being of the opposite sex.
"Um, maybe that's because men rape and women don't?" Spastic feminists. Like checking some babe out is just a hop, skip, and a jump from brutish violation.
Polish victims of Jewish control had a saying that "The Jew cries while he beats you." The same applies to mainstream feminism since the '90s, droning on about the Madonna/Whore Dichotomy while launching and inflaming a witch hunt to suppress all expression of a healthy male sex drive.